IS 3708 (Part 1) : 2013 ISO 126 : 2005

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Indian Standard METHODS OF TEST FOR NATURAL RUBBER LATEX
PART 1 DETERMINATION OF DRY RUBBER CONTENT [NRL : 1]

( Second Revision )

ICS 83.040.10

© BIS 2013

BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 April 2013 Price Group 3

Rubber and Rubber Products Sectional Committee, PCD 13

NATIONAL FOREWORD This Indian Standard (Part 1) (Second Revision) which is identical with ISO 126 : 2005 `Natural rubber latex concentrate -- Determination of dry rubber content' issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Rubber and Rubber Products Sectional Committee and approval of the Petroleum, Coal and Related Products Division Council. This standard was first published in 1966 and then revised in 1985. The committee has decided to revise this standard to completely align it with ISO 126 : 2005 and publish under dual numbering system. Other standards on methods of tests are given in National Annex A at the end of this publication. The text of ISO Standard has been approved as suitable for publication as an Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following: a) Wherever the words `International Standard' appear referring to this standard, they should be read as `Indian Standard'. b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a point (.) as the decimal marker. In this adopted standard, reference appears to certain International Standards for which Indian Standards also exist. The corresponding Indian Standards which are to be substituted in their respective places are listed below along with their degree of equivalence for the editions indicated: International Standard Corresponding Indian Standard Degree of Equivalence Identical ISO 123 : 2001 Rubber latex -- IS 9316 (Part 5) : 2012 Methods of Sampling test for rubber latex: Part 5 Drawing of samples [RL : 5] (second revision) ISO 124 : 2008 Latex, rubber -- IS 9316 (Part 4) : 2012 Methods of Determination of total solids content test for rubber latex: Part 4 Determination of total solids content [RL : 4] (second revision)

Identical

The technical committee has reviewed the provision of the following International Standard referred in this adopted standard and has decided that it is acceptable for use in conjunction with this standard: International Standard ISO/TR 9272 : 2005 Title Rubber and rubber products -- Determination of precision for test method standards

In reporting the result of a test or analysis made in accordance with this standard, if the final value, observed or calculated, is to be rounded off, it shall be done in accordance with IS 2 : 1960 `Rules for rounding off numerical values (revised)'.

IS 3708 (Part 1) : 2013 ISO 126 : 2005

Indian Standard METHODS OF TEST FOR NATURAL RUBBER LATEX
PART 1 DETERMINATION OF DRY RUBBER CONTENT [NRL : 1]

( Second Revision )
WARNING -- Persons using this International Standard should be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.

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Scope

This International Standard specifies a method for the determination of the dry rubber content of natural rubber latex concentrate. The method is not necessarily suitable for latices preserved with potassium hydroxide, latices from natural sources other than Hevea brasiliensis, or for compounded latex, vulcanized latex or artificial dispersions of rubber and it is not applicable to synthetic rubber latices.

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Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including amendments) applies. ISO 123, Rubber latex -- Sampling ISO 124, Latex, rubber -- Determination of total solids content ISO/TR 9272, Rubber and rubber products -- Determination of precision for test method standards

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Terms and definitions

For the purposes of this document, the following terms and definitions apply. 3.1 natural rubber latex concentrate natural rubber latex containing ammonia and/or other preservatives and which has been subjected to some process of concentration

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Principle

A test portion of latex concentrate is diluted to 20 % (by mass) total solids content and acidified with acetic acid. The coagulated rubber is then formed into a sheet and dried at 70 °C 5 °C.

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IS 3708 (Part 1) : 2013 ISO 126 : 2005

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Reagents

During the analysis, use only reagents of recognized analytical quality and only distilled water or water of equivalent purity. 5.1 Acetic acid, 20 g/dm3 aqueous solution, for use with latex concentrate preserved with ammonia.

5.2 Acetic acid, 50 g/dm3 solution in aqueous propan-2-ol, prepared by adding 50 g of glacial acetic acid to 500 cm3 of propan-2-ol and then diluting the resultant solution to 1 dm 3 with water. For use with latex concentrate preserved with potassium hydroxide. 5.3 Ethanol, 95 % (by volume).

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Apparatus

Standard laboratory apparatus plus the following: 6.1
NOTE

Dish, preferably made of glass or porcelain, approximately 100 mm in diameter and 50 mm deep.
Dishes made of aluminium are unsuitable for use with latex concentrate containing potassium hydroxide.

6.2 6.3

Balance, capable of weighing to an accuracy of 1 mg. Circulating-air oven, capable of maintaining a temperature of 70 °C 5 °C.

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Sampling

Carry out sampling in accordance with one of the methods specified in ISO 123.

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8.1 8.2

Procedure
If the total solids is not known, determine it in accordance with ISO 124. Carry out the procedure in duplicate.

8.3 Weigh by difference from a conical flask fitted with a stopper, to the nearest 1 mg, 10 g 1 g of latex concentrate into the dish (6.1). Pour sufficient water down the inside edge of the dish to reduce the solids content of the latex concentrate to (20 1) % (by mass). Carefully rotate the dish on a smooth surface to dilute the latex and ensure homogeneity. Proceed in accordance with 8.4 or 8.5 as appropriate, depending on whether the latex concentrate is preserved with ammonia or potassium hydroxide, respectively. 8.4 In the case of latex concentrate preserved with ammonia, add, over a period of 5 min, 35 cm3 5 cm3 of 20 g/dm3 acetic acid solution (5.1), pouring it down the inside edge of the dish and slowly rotating the dish while the acid is being added. Gently depress the coagulated sheet of rubber below the surface of the acid. Cover the dish with a watch glass and heat on a steam bath for 15 min to 30 min. If the serum remains milky, add 5 cm3 of 95 % (by volume) ethanol (5.3). Continue as described in 8.6. 8.5 In the case of latex concentrate preserved with potassium hydroxide, add 25 cm3 5 cm3 of 50 g/dm3 acetic acid solution (5.2). Mix the acidified latex by means of a thin glass rod and wash any latex concentrate remaining on the rod into the dish with a little water. Gently depress the coagulated sheet of rubber below the surface of the acid. Cover the dish with a watch glass and heat on a steam bath for 15 min to 30 min.

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IS 3708 (Part 1) : 2013 ISO 126 : 2005
8.6 When the serum is clear, collect any small particles of coagulated rubber by rubbing with the main bulk. Soak the coagulated rubber in several changes of water until the water is no longer acidic to litmus. Press the coagulated rubber to expel water and obtain a uniform sheet not exceeding 2 mm in thickness. A convenient method is to place the coagulated rubber carefully on a glass plate and with a glass stopper about 45 mm in diameter, or a small photographic roller, to press first around the circumference and then work towards the centre. Rinse the sheet thoroughly in running water for at least 5 min in the case of latex concentrate preserved with ammonia, or at least 2 h in the case of latex concentrate preserved with potassium hydroxide. Allow the rinsed sheet to drip for a few minutes before transferring it to the drying oven (6.3). 8.7 Dry the sheet at a temperature of 70 °C 5 °C until it has no white patches. If the sheet is dried on a watch glass, carefully turn it over two or three times during the first few hours of drying. Allow to cool in a desiccator for 30 min and weigh. Repeat the operation of drying, cooling and weighing until the loss in mass is less than 1 mg after heating for 30 min. If the sheet becomes excessively sticky and it is suspected that significant oxidation is taking place at 70 °C, then use a lower drying temperature, for example 55 °C.

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Expression of results

9.1 Calculate the dry rubber content (DRC) of the latex concentrate as a percentage by mass to the second decimal place from the equation:

DRC where

m1 m0

100

m0 is the mass, in grams, of the test portion; m1 is the mass, in grams, of the dry sheet. 9.2 The results of the duplicate determinations shall agree to within 0,1 % (by mass) of the mean value. If they do not, repeat the determination. Report the mean value.

10 Precision statement
10.1 The precision of this method was determined in accordance with ISO/TR 9272. Please refer to this document for terminology and explanations of statistical concepts. The precision results are given in Table 1. The precision parameters shall not be used for acceptance or rejection of any group of materials without documentation that the parameters are applicable to the particular group of materials and the specific test protocols of this test method. The precision is expressed on the basis of a 95 % confidence level for the values established for repeatability r and reproducibility R. 10.2 The results contained in Table 1 are average values and give an estimate of the precision of this test method as determined in an inter-laboratory test programme (ITP) conducted in 2001. Thirteen laboratories performed triplicate analyses on two samples, A and B, which were prepared from high-ammonia latex. Before the bulk was sub-sampled into 1-litre bottles labelled A and B, it was filtered and homogenized by thorough blending and stirring. Thus, essentially, samples A and B were the same and were treated as such in the statistical computations. Each participating laboratory was required to carry out the test using these two samples on the dates which had been given to the participants in the ITP. 10.3 A Type 1 precision was determined (the test samples used for the ITP were distributed in the prepared state, ready for testing).

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IS 3708 (Part 1) : 2013 ISO 126 : 2005
10.4 Repeatability: The repeatability r (in measurement units) of this test method has been established as the appropriate value tabulated in Table 1. Two single test results, obtained in the same laboratory under normal test conditions, that differ by more than the tabulated value of r (for any given level) shall be considered to have come from different (non-identical) sample populations. 10.5 Reproducibility: The reproducibility R (in measurement units) of this test method has been established as the appropriate value tabulated in Table 1. Two single test results, obtained in two different laboratories under normal test conditions, that differ by more than the tabulated value of R (for any given level) shall be considered to have come from different (non-identical) sample populations. 10.6 Bias: In test method terminology, bias is the difference between an average test value and the reference (or true) test property value. Reference values do not exist for this test method since the value (of the test property) is exclusively defined by the test method. Bias, therefore, cannot be determined for this particular test method. Table 1 -- Estimate of precision for DRC test method
Average 60,26
r 2,83 sr

Within lab sr 0,029 r 0,06

Between labs sR 0,046 R 0,13

where r is the repeatability (in measurement units) and sr is the within-laboratory standard deviation. R 2,83 sR

where R is the reproducibility (in measurement units) and sR is the between-laboratory standard deviation.

11 Test report
The test report shall include the following particulars: a) b) c) d) e) f) a reference to this International Standard; all details necessary for the identification of the test sample; the mean value of the dry rubber content (DRC) of the latex concentrate, quoted to the nearest 0,01 % (by mass); the drying temperature, if other than 70 °C 5 °C;

any unusual features noted during the determination; details of any operation not included in this International Standard or in the International Standards to which reference is made, as well as details of any operation regarded as optional.

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IS 3708 (Part 1) : 2013 ISO 126 : 2005

NATIONAL ANNEX A (National Foreword)
For proper referencing, a table showing correspondence of the previous test methods and with the present have been given in Table 1 below: Table 1 Correspondence of the Various Methods of Test Covered in the Existing Series of IS 3708, IS 4511 and IS 9316 With Those in the Old Series
Old Test Methods Test Method (1) RL SERIES Determination of surface tension Determination of viscosity Determination of coagulum content Determination of total solids content Drawing of samples Determination of pH Determination of total copper Determination of total iron Determination of total manganese NRL SERIES Determination of dry rubber content Determination of sludge content Determination of density Determination of total alkalinity Determination of KOHnumber Determination of mechanical stability Determination of volatile fatty acid number Determination of total nitrogen Determination of total ash Determination of boric acid Determination of magnesium SBRL SERIES Determination of dry polymer Determination of density Determination of residual styrene (volatile unsaturates) Determination of bound styrene Determination of soap content Determination of high speed mechanical stability IS 4511 : 1967 IS 4511 : 1967 IS 4511 : 1967 Part 1 [SBRL : 1] Part 1 [SBRL : 6] Part 1 [SBRL : 8] IS 4511 (Part 1) : 1986 IS 4511 (Part 2) : 1986 IS 4511 (Part 3) : 1987 SBRL : 1 SBRL : 6 SBRL : 8 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1968 IS 3708 : 1968 Part 1 [NRL : 1] Part 1 [NRL : 5] Part 1 [NRL : 6] Part 1 [NRL : 7] Part 1 [NRL : 8] Part 1 [NRL : 9] IS 3708 (Part 1) : 1985 IS 3708 (Part 2) : 1985 IS 3708 (Part 3) : 1985 IS 3708 (Part 4) : 1985 IS 3708 (Part 5) : 2005 IS 3708 (Part 6) : 1985 IS 3708 (Part 7) : 2005 IS 3708 (Part 8) : 2005 IS 3708 (Part 9) : 2005 IS 3708 (Part 10) : 1986 IS 3708 (Part 11) : 2001 NRL : 1 NRL : 5 NRL : 6 NRL : 7 NRL : 8 NRL : 9 NRL : 10 NRL : 12 NRL : 16 NRL : 17 NRL : 18 IS 9316 : 1979 IS 9316 : 1979 IS 9316 : 1979 IS 9316 : 1979 IS 9316 : 1979 IS 9316 : 1982 IS 3708 : 1966 IS 3708 : 1966 IS 3708 : 1966 Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 1 [NRL : 13] Part 1 [NRL : 14] Part 1 [NRL : 15] IS 9316 (Part 1) : 1987 IS 9316 (Part 2) : 1987 IS 9316 (Part 3) : 1987 IS 9316 (Part 4) : 1988 IS 9316 (Part 5) : 1988 IS 9316 (Part 6) : 1988 IS 9316 (Part 7) : 1987 IS 9316 (Part 8) : 1987 IS 9316 (Part 9) : 1987 RL : 1 RL : 2 RL : 3 RL : 4 RL : 5 RL : 6 RL : 7 RL : 8 RL : 9 IS No. (2) Part (Series) (3) Existing Test Methods IS No. (4) Series (5)

Part 1 [NRL : 10] Part 1 [NRL : 12] Part 1 [NRL : 16] Part 2 [NRL : 17] Part 2 [NRL : 18]

IS 4511 : 1967 IS 4511 : 1967 --

Part 1 [SBRL : 9] Part 1 [SBRL : 10] --

IS 4511 (Part 4) : 1986 IS 4511 (Part 5) : 2005 IS 4511 (Part 6) : 1987

SBRL : 9 SBRL : 10 SBRL : 11

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